Communication technology has made a progress by being divided into a cable transmission technology mainly providing a data service and a wireless transmission technology focusing on a speech service. Recent progress in high-speed wireless transmission technology and cable network infrastructure contributes to the continuous development of cable and wireless integrated technologies that can provide a data service while securing mobility. The cable-wireless integrated technology can provide users with a variety of services with no regional restriction.
Meanwhile, broadcasting technology is undergoing a dramatic change from analog scheme to digital scheme. The change in the broadcasting technology has made it possible to provide users with even more abundant sorts of services such as bi-directional broadcasting service and additional services as well as typical real-time broadcasting services. A broadcasting system occupies one axis of information infrastructure in combination with a communication system, such as cable and wireless internet. A broadcasting system and a communication system, which used to be separate systems independent from each other, are organically combined with each other and make advances.
Generally, broadcasting-communication system exists in the form of diverse systems developed to provide diverse services. The data transmission rate of the broadcasting-communication system is determined according to the standard of a corresponding technological area. For example, the standard data transmission rate of the Advanced Terrestrial Systems Committee (ATSC) 8-Vestigial Sideband (VSB) is 19.39 Mbps at 6 MHz band, whereas the standard data transmission rate of Digital Video Broadcasting-Terrestrial (DVB-T) ranges from at least 4.354 Mbps up to 27.710 Mbps at 7 MHz band. Also, the standard data transmission rate of the Terrestrial-Digital Multimedia Broadcasting (T-DMB) is 1.125 Mbps at 1.536 MHz band.
Meanwhile, development of diverse services and contents produces services of a new concept such as a data broadcasting service, a non-real time (NRT) service, a disaster alert service and so forth. This calls for technical schemes that can support and transmit the additional services. Conventional broadcasting-communication system uses a method of reducing the data transmission rates of an original service and allocating a new service to the reserved data transmission rate. In other words, some of the bandwidth to be allocated to the original service is allocated to an additional service. As a result, the bandwidth to be allocated to the original service is reduced. In an ATSC 8-VSB system, among 19.39 Mbps allocated to a High-Definition (HD) broadcasting, about 2 Mbps is allocated to a new additional service such as a data broadcasting, and the remaining 17.4 Mbps is allocated to the original HD broadcasting service. Since this method reduces the data transmission rate of the original service to transmit the new additional service, there is a drawback in that the quality of the original service is deteriorated. Therefore, it is required to develop a data transmission method that can transmit additional data without affecting the transmission of original data.